Development of Specific & High Affinity Polymer-binding Peptides for Microplastic Identification and for Enhanced Enzymatic Degradation

Microplastic pollution is one of the most pressing problems of our time. There are innumerable sources of microplastic including the production of fine particulates as a by-product of various industrial processes. These particles mainly end up in landfills where they are released into the environment. Efficient recycling of these materials reduces microplastic pollution and saves primary resources for polymer production. However, economically and ecologically relevant recycling technologies for fine polymer particles are not yet established. The aim of the presented work is to provide methods for rapid and simple analysis of complex environmental samples and the optimization of particle degradation. These methods will be based on low-cost and environmentally friendly peptides that bind specifically and with high affinity to polyethylene terephthalate (PET), polyamide and polyurethane, respectively. To identify the peptides, phage surface display (PSD) is performed on micrometer-sized polymer particles. Eight putative PET binding phages were already identified by PSD using PET particles as target material. In future, isothermal titration calorimetry will be used to determine the thermodynamic parameters of the peptide-polymer interaction. To identify the chemical groups involved in binding, fourier-transformed infrared spectroscopy along with alanine scanning mutagenesis will be utilized. Upon optimization, the developed polymer-binding peptides will be heterologously expressed with different fluorescent labels. Flow cytometry will be used for the analysis and sorting of fluorescently marked particles. Cooperation partners at the Helmholtz Center Berlin will produce hybrids of the developed polymer-binding peptides and polymer-degrading enzymes to enhance enzyme-particle affinities resulting in improved polymer degradation.